Hello, my name is Andrés and I'm in Argentina. My grandfather asked my help just in case I might get lucky finding what he needs. He has a R.B. Auto Graflex camera, for 4x5 inches, but it's missing the curtain. He told me that curtain allows from 1/10 to 1/1000 of a second, and that you can take vertical or horizontal pictures with it.
Please excuse my lack of technical english about this topic. He's 83 years old now and fixing that camera is really important for him. Please if you need any more info just ask and I'll try to get it. I'm also attaching a scan of a photo he took of the camera's plate, just in case it serves.